Radiant energy – Invisible radiant energy responsive electric signalling – With radiant energy source
Reexamination Certificate
2001-07-31
2004-04-06
Hannaher, Constantine (Department: 2878)
Radiant energy
Invisible radiant energy responsive electric signalling
With radiant energy source
C250S397000, C250S492300
Reexamination Certificate
active
06717154
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to the assessment or quantitative evaluation of the amount of radiation delivered to an object undergoing sterilization in situ.
BACKGROUND OF THE INVENTION
Providing a food supply that is safe for consumption can be problematic, particularly because suitable control measures can be hard to enforce as the producers, distribution chains, and markets become more global. In addition, visual inspections are not always reliable as a means of detecting harmful contaminants. Further, cross contamination of foods can occur during handling (including during harvesting, shipping, and packaging), that can infect food typically believed to be relatively safe from pathogens. For example,
E. coli
bacteria, which is typically found in certain meats, can also be found in “fresh” vegetables and fruits. The presence of atypical bacteria in foods can be attributed to the use of particular types of fertilizers or to processing conditions. Certain processing conditions may allow direct contact of various food items with contaminated products, while others may allow for indirect contamination such as via contact with contaminated containers or work surfaces, each of which can allow the undesirable spreading of contaminants.
Certain safety precautions can be taken to reduce the risk of illness associated with the consumption of foods which may carry pathogens, such as washing the fruit and vegetables before consumption and/or cooking meat or other food items to or above a certain temperature. While washing vegetables and fruits can dilute or remove the contaminant(s) from the food, and cooking the food to a temperature sufficient to kill the bacteria may reduce the exposure risk, not all foodstuffs are washed or properly cooked before they are eaten. Further, children can be especially vulnerable to harmful exposures, as many do not reliably pursue these safety measures and exposure to relatively small amounts of harmful contaminants can be more profound relative to healthy adults. A consumer has little control over what safety steps (i.e., washing and/or cooking food properly), are followed by personnel at a food service outlet.
Processing foods to reduce or even eliminate unwanted microorganisms can be an important step forward in the reduction and elimination of the risk of illness due to exposures to contaminated foods. One economic and effective way to rid food of contaminating microorganisms is to irradiate food with ionizing radiation to effectively “sterilize” the food to destroy the harmful microorganisms therein (irradiation can be used to sterilize other objects such as medical devices). This can be an effective and economic tool in improving the safety of the food supply to thereby provide safe, sterilized food items which have reduced (and potentially even undetectable) levels of harmful microorganisms.
Generally stated, there are two primary modalities used to irradiate food and other items to achieve sterilization. One modality includes the use of a radioactive element such as Cobalt-60, and the other employs electron beams produced by a linear accelerator. The radiation dose should be monitored to ensue that pathogens are destroyed effectively. For food or edible items, radiation doses in the 0.15 kGy to 10 kGy range are typically used, while for devices and objects, radiation doses are higher, typically up to 20 kGy or more.
Conventionally, in order to monitor the radiation doses provided by the irradiation process, either TLD's (thermoluminescent devices) or chromatic tags are used. TLD's can be generally described as crystals, e.g., lithium fluoride, the structure of which is changed (damaged) during exposure to radiation. More particularly, during irradiation, electrons travel to and are trapped in the crystal after being ejected by the high-energy (ionizing) photons used for sterilization. Upon exposure to heat, the electrons in the crystal fall back to their ground states and emit light as result of the change. A spectrophotometer is used to measure this light and provide a quantitative assessment of the amount of radiation to which the device was exposed. A technician typically recovers the TLD from an irradiated package and then analyzes/measures the emitted light on the spectrophotometer. Unfortunately, this process can be relatively labor-intensive and can be undesirable for use in a mass production environment.
Chromatic tags can be described as plastic tags (formed of materials such as PMMA) which undergo a color change upon exposure to radiation at some level. However, generally stated, the color change is often a subjective evaluation when done visually by an inspector. To receive a more reliable assessment, colormetric readers are used to quantify the color change to a more exact level. This can be compared to the use of radiographic film wherein the level of exposure on the film corresponds to the intensity of the dose received. Unfortunately, again, the determination of the dose measured in this manner can also be labor intensive and/or unsuitable for a mass-production environment.
OBJECTS AND SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a cost-effective dosimeter, which can be used to evaluate the radiation dose delivered to an item undergoing sterilization.
It is yet another object of the present invention to provide improved methods to evaluate a radiation dose(s) delivered to a plurality of sterilized packaged food items without requiring direct human intervention.
It is a further object of the present invention to provide economic methods and devices which are suitable for mass-production environments and which can automatically relay and/or correlate production and/or process information to an irradiation dose.
It is an additional object of the present invention to provide an economic automated method of determining the amount of radiation delivered to an item in situ.
It is another object of the present invention to provide an economic dosimeter configuration, the sensing element of which can be embedded in a packaged and/or sealed food or medical item.
These and other objects can be satisfied by the present invention by a radiation dosimeter which is adapted to change the value of an associated electronic parameter in a detectable manner dependent upon the amount of radiation it is exposed to. The value of the electronic parameter can be relayed automatically (or semi-automatically) and used to determine and provide the radiation dose for a sterilized item, preferably a food or edible item, without requiring human intervention. The sensor can be configured as a single use, disposable, passively operated wireless or telemetrically operated sensor.
More particularly, a first aspect of the invention is a method for determining the irradiation dose delivered to an object. The method includes the steps of (a) irradiating at least one object with a radiation dose which is sufficient to sterilize the object; (b) positioning a sensor on the object such that it is held proximate the object during the irradiating step, the sensor has associated operational parameters, and one or more of the operational parameters is configured to change responsive to the irradiating step; (c) transmitting data associated with the operational change in the parameter of the sensor; and (d) determining the radiation exposure dose based on the data provided by the transmitting step. In certain embodiments, the transmitting step can be performed such that is carried out by a wireless or telemetric transmission.
A second aspect of the present invention is a radiation dose evaluation system. The system includes a radiation source and at least one dosimeter sensor adapted to be positioned on an object undergoing irradiation treatment such that the sensor is exposed to an amount of radiation representative of the amount of radiation exposure introduced to the object. The system also includes a wireless or telemetric reader operably associated with the sensor such that it receive
Black Robert D.
Mann Gregory Glenwood
Widener Steven R.
Gabor Otilia
Hannaher Constantine
Myers Bigel & Sibley Sajovec, PA
Sicel Technologies, Inc.
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